Improve AttributedString.CharacterView to Substring conversion in AttributedStringProtocol.range(of:) (#1440)

Author: jmschonfeld

Benchmarks/Benchmarks/AttributedString/BenchmarkAttributedString.swift

@@ -63,9 +63,9 @@ let benchmarks = {
     Benchmark.defaultConfiguration.metrics = [.cpuTotal, .wallClock, .throughput]
 
     let manyAttributesString = createManyAttributesString()
+    let longString = createLongString()
 #if FOUNDATION_FRAMEWORK
     let manyAttributesNS = createManyAttributesNSString()
-    let longString = createLongString()
     let toInsertNS = NSAttributedString(string: String(repeating: "c", count: longString.characters.count))
 #endif
 
@@ -509,6 +509,10 @@ let benchmarks = {
             blackHole(value)
         }
     }
+    
+    Benchmark("range(of:)") { benchmark in
+        longString.range(of: "cccc")
+    }
 }
 
 

Sources/FoundationEssentials/AttributedString/AttributedStringProtocol.swift

@@ -267,7 +267,7 @@ extension AttributedStringProtocol {
     internal func _range<T: StringProtocol>(of stringToFind: T, options: String.CompareOptions = []) -> Range<AttributedString.Index>? {
 
         // TODO: Implement this on BigString to avoid O(n) iteration
-        let substring = Substring(characters)
+        let substring = Substring(String(_characters: self.characters))
         guard let range = try? substring._range(of: Substring(stringToFind), options: options) else {
             return nil
         }